Cannot resolve method ‘findViewByID(int)’ in Android Studio

I only just started coding for androud, but I’ve been getting the error: “Cannot resolve method ‘findViewByID(int)'” in android studio

I can’t seem to find out what is wrong, have tried setting contentView, implementing OnClickListenener, but none of these fixed anything.

full code below, the MainActivity Method is where it all happens:

package aprivate.contract.jdeko.dww_registration;

import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.view.View.OnClickListener;

import com.google.android.gms.appindexing.Action;
import com.google.android.gms.appindexing.AppIndex;
import com.google.android.gms.common.api.GoogleApiClient;


public class MainActivity extends AppCompatActivity{
    private GoogleApiClient client;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button clickButton = (Button) findViewByID(R.id.Btn);
        clickButton.setOnClickListener( new OnClickListener() {

            @Override
            public void onClick(View v) {
             //todo
            }
        });
    }

    @Override
    public void onStart() {
        super.onStart();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        client.connect();
        Action viewAction = Action.newAction(
                Action.TYPE_VIEW, // TODO: choose an action type.
                "Main Page", // TODO: Define a title for the content shown.
                // TODO: If you have web page content that matches this app activity's content,
                // make sure this auto-generated web page URL is correct.
                // Otherwise, set the URL to null.
                Uri.parse("http://host/path"),
                // TODO: Make sure this auto-generated app URL is correct.
                Uri.parse("android-app://aprivate.contract.jdeko.dww_registration/http/host/path")
        );
        AppIndex.AppIndexApi.start(client, viewAction);
    }

    @Override
    public void onStop() {
        super.onStop();

        // ATTENTION: This was auto-generated to implement the App Indexing API.
        // See https://g.co/AppIndexing/AndroidStudio for more information.
        Action viewAction = Action.newAction(
                Action.TYPE_VIEW, // TODO: choose an action type.
                "Main Page", // TODO: Define a title for the content shown.
                // TODO: If you have web page content that matches this app activity's content,
                // make sure this auto-generated web page URL is correct.
                // Otherwise, set the URL to null.
                Uri.parse("http://host/path"),
                // TODO: Make sure this auto-generated app URL is correct.
                Uri.parse("android-app://aprivate.contract.jdeko.dww_registration/http/host/path")
        );
        AppIndex.AppIndexApi.end(client, viewAction);
        client.disconnect();
    }

}

Answer

It’s just a typo that you have made. You should use “Id” instead of “ID”.

So your

Button clickButton = (Button) findViewByID(R.id.Btn);

Becomes

Button clickButton = (Button) findViewById(R.id.Btn);